It is known to implant medical devices constituted by inflating banding rings, around blood vessels of patients in order to restrict blood flow, for example on the pulmonary arteries. This is the subject of the patent application US2008/0097947A which discloses an annular banding device for the pulmonary artery, comprising an inflating banding ring intended to be put in place around the pulmonary artery of the patient, an inflation tube connecting the banding ring to an insufflating button. The banding ring is generally C-shaped and comprises an external thin rigid silicone layer and an internal thin silicone layer, forming an inflating balloon. The rigid silicone external layer or wall extends into the end zone corresponding to the opening of the “C” so as to form locking means making it possible to adapt the inflation bandage device to the diameter of the pulmonary artery. The ring also comprises holes for the passage of sutures allowing it to be fixed to the pulmonary artery of the patient. The inflation of this ring leads to the deformation of the thin flexible silicone inside wall in a centripetal direction, which causes a compression of the pulmonary artery and a reduction in its inner diameter. The inflation is carried out using a liquid which is injected using the insufflating button which can also be pulled to allow deflation of the ring.
This type of inflatable vascular ring exists not only in cardiac surgery but also in hepatic surgery. Thus the PCT application WO2010/102661A describes an implant for controlling the blood flow inside a vessel, namely more precisely the portal vein. This control is particularly critical for the success of liver transplants and major hepatectomies. In fact, it is vital for the patient that blood flow in the portal vein just after the transplantation or hepatectomy is not excessive, at the risk of unacceptably damaging the hepatic graft. This phenomenon is known by the name of “Small For Size (SFS)” syndrome. This syndrome occurs in the case of a portal flow rate greater than 260 ml/min per 100 g of liver and/or a portal pressure greater than 20 mm Hg. It causes a lethal alteration of the liver.
The perivascular adjustable implant according to WO2010/102661A comprises an inflatable balloon (3) of open annular shape, arranged inside a non-extendible band (4). The inflation balloon is connected to an injection chamber by an inflation tube. The non-extendible outer band is equipped with locking means (6) of the ring or vessel. The inflation and the deflation of the annular inner balloon makes it possible to restrict (inflation) or increase (deflation) the inner diameter of the vessel around which the implant is placed. This implant comprises, on the inside of the inflatable balloon, means for measuring the blood pressure inside the vessel. FIGS. 2A to 2D of WO2010/102661A show the change in shape of the inflatable balloon as it is inflated. It appears that the inner wall of the inflatable balloon changes from a circular shape (FIG. 2A) to a shape leaving a passage by growing, which is caused by a bulge in the inflation balloon. It is clear that such a compression of the portal vein is equivalent to crushing, causing a stenosis which leads to turbulences in the blood flow resulting in risks of thrombosis.
This implant according to WO2010/102661A does not therefore allow satisfactory control of the flow rate and/or of the blood pressure inside the vessels, in particular the portal vein. This implant does not provide an effective solution to the problem of SFS syndrome, after a hepatectomy or a liver transplant.